Experimental Investigation on the Influence of a Hollow Rotor Shaft Cooling and Oil Properties on No-Load Losses in Traction Electric Machines

This study contributes to the evaluation of thermal management strategies and losses mitigation in traction electric machines and provides valuable insights for engineers and researchers striving to optimize machine performance. Direct and indirect oil cooling strategies as well as increased rotational speeds have become mandatory to support the growing need for more power dense electric machines. For traction applications, reducing losses on low and no-load operating points is crucial for optimizing the energy consumption on reference vehicle duty cycles. In addition, rotor losses can become quite high as rotational speed increases. Therefore, the focus of this study is on the rotor shaft cooling and oil properties influence on no-load losses. In this paper, multiple parameters are tested (oil type, temperature, flow rate) on a dedicated electric machine prototype and the influence on no-load losses is analyzed.